1. Field of the Invention
The invention relates to a method for obtaining a solution of nuclear fuel not readily dissolvable, especially of PuO.sub.2 or (U/Pu)O.sub.2 mixed oxide in nitric acid within an airtight sealed vessel (autoclave).
2. Description of the Prior Art
A method of dissolving nuclear fuel is disclosed in European Patent No. 00 49 827 and equivalent U.S. Pat. No. 4,528,130. According to this method a suspension of PuO.sub.2 or (U/Pu)O.sub.2 mixed oxide in concentrated nitric acid is heated in an autoclave. The nitric acid together with the nuclear fuel is stirred and mixed inside the airtight closed autoclave. The temperature of the nuclear fuel and the nitric acid advantageously is the same or higher than the boiling temperature of nitric acid at normal pressure (atmospheric pressure).
With this method, for example, 4 g PuO.sub.2 in 30 ml concentrated nitric acid could be dissolved at approximately 200.degree. C. in about 20 hours. This resulted in a final concentration of 130 g plutonium per liter of solution.
Considerably higher plutonium contents in the solution cannot be obtained with the known method, because the solution rate drops toward zero given a stronger concentration of plutonium in the solution.